Effects of virtual reality erotica on ejaculate quality of sperm donors: a balanced and randomized controlled cross-over within-subjects trial

Background Previous research has shown that the type and duration of erotic material that men have access to during masturbation can influence semen parameters. To our knowledge, the use of virtual reality (VR) headsets to present erotica has not previously been studied. We reasoned that, because VR can provide a more immersive experience to the user, semen parameters of masturbatory ejaculates may be altered. Methods This study had a balanced and randomized controlled cross-over within-subjects design. 504 ejaculates were collected from 63 sperm donors at 4 locations in Denmark. During masturbation each donor was instructed to observe erotic material either on a touch screen monitor or using a VR headset. The order of each pair of within-subject treatments was randomized by the throw of a dice. Anonymized data were analysed with linear mixed and piecewise structural equation models. Results Both abstinence period and VR-use influenced the total number of motile spermatozoa ejaculated. For short abstinence periods, VR-use increased the number of motile sperm in the ejaculate. However, the difference between VR and non-VR ejaculates decreased as abstinence period increased such that there was no difference at the mean abstinence period of 58 h. For longer abstinence periods, total motile sperm counts were lower, on average, when men used VR compared to those that did not. Conclusion The use of VR headsets to view erotica had a strong positive effect on the number of motile sperm in an ejaculate when the donor’s abstinence time was short (< 24 h). VR-use could improve the ejaculate quality of men who are asked to provide samples after a short period of abstinence, such as men in infertile partnerships producing samples for ART or cancer patients depositing sperm before treatment

From a port for traders to a town of merchants: exploring the topography, activities and dynamics of early medieval Copenhagen

Copenhagen’s earliest history has long been shrouded in uncertainties. This is mainly due to insufficient source material. Basic questions – how old is the town, how did it originate, and where was the oldest settlement situated? – are still under discussion, as are questions regarding specific features of the early medieval town. Was Absalon’s twelfth-century castle preceded by an earlier one? What does a centrally placed, early medieval horseshoe-shaped enclosure surrounded by a massive ditch represent? Using archaeological results from recent major excavations, combined with Bayesian modelling of new 14C dates from the two early cemeteries of Sankt Clemens and Rådhuspladsen, older archaeological information and the medieval written sources on Copenhagen are revisited to form a new interpretation of the early development of the town. Three phases of topographical development from the eleventh to the early thirteenth century are recognised. The changes tell of a dynamic first two hundred years of the town’s history and of its changing role in Danish society. The article explores the people, activities and networks that lie behind the outstanding development from the small early settlement of the eleventh century to the flourishing merchant town of the thirteenth century